1. Field of the Invention
The present invention relates to thermoplastic molding compositions and more particularly, to thermoplastic shapable blends of an ethylene-acrylic acid copolymer and a polyester ether based on 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol and poly(oxytetramethylene) glycol.
2. Discussion of the Background
Polyester-ethers such as those described in U.S. Pat. No. 4,349,469 possess good melt strength and are particularly valuable for use in the manufacture of extrusion blow molded objects. For example, such polyester-ethers can be extruded downward in the shape of a hollow cylinder. Containers can be formed by clamping a mold around the molten cylinder and subjecting the hollow cylinder to internal pressure to form a bag or similar article. Bags manufactured from polyester-ethers are suitable for the packaging sterile pharmaceutical solutions intender for intravenous administration.
Polyester-ether bags manufactured for packaging intravenous solutions typically must be packaged in an overwrap of high density polyethylene or coated with a poly(vinylidene chloride) polymer latex to reduce the water vapor transmission rate. Rather than using the known overwrap or coating techniques, it would be advantageous if the polyester ethers could be blended with another polymer which would impart the desired low water vapor transmission rate to the resulting polymer blend. However, most polymers capable of decreasing the water vapor transmission rate of polyester-ethers are not compatible with the polyester-ethers as evidenced by the optical characteristics, i.e., poor clarity or haze, of films and bags prepared from blends of polyester-ethers with the incompatible polymers Good optical clarity is essential to allow observation or inspection of the contents of the bag. Good clarity also is critical for a variety of other types of packaging and medical applications for which polyester-ethers are suited.